Commutator.



1 u Ah mmmm PATENTED MAY 28, 1907.

L. B. UNDERWOOD.

COMMUTATOR.

APPLICATION FILED we. 9, 1905.

Inventor Louis E. Underw 00d by M4 Witnesses:

UNITED STATES PATENT OFFICE.

LOUIS E. UN DERVVOOD, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

COMMUTATOR.

Specification of Letters Patent.

Tatented May 28, 1907.

Application filed August 9, 1005. Serial No. 273,889.

To all whom it may concern.-

Be it known that I, Louis E. UNDERWOOD,

a citizen of the United States, residing at Lynn, county of Essex, Stateof Massachusetts, have invented certain new and useful Improvements inCommutators, of which the following is a specification.

Heretofore a large proportion of all commutators for dynamo electricmachines in general use have been made with sheet mica as the insulatingmaterial between adjacent conducting segments. Sheet mica is anexcellent insulator, is not affected by moisture, and possesses featuresof mechanical strength and rigidity which fit it for such use. Thismaterial, however, possesses the disadvantage for the purpose in hand,of being comparatively expensive, and the further disadvantage thatunder many conditions of service, owing to its toughness, it is not wornaway by the brushes as rapidly as are the commutator segments proper.This results in the fault known as high mica in which the outer edges ofthe insulation between the segments of a commutator which has been inservice for some time project above the surface of the commutator,thereby causing sparking between the commutator and its brushes, andother troubles.

I have found that excellent results may be obtained by the use ofinsulating material such as sheet mica, or some other and preferablyless expensive substance, such as leather board, possessing the properinsulating and physical properties, which may well be tougher than mica,as the means for mechanically separating the contact bars, when suchinsulation is so arranged and disposed that it does not come intoengagement with the brushes in the normal operation of the com mutator.

In carrying out my invention I arrange the insulation between anadjacent pair of commutator bars in two portions, one pottion separatingthe outer portions of the conduotor bars extending from the outersurface of the commutator to a depth substantially equal to the wearingdepth of the commutator bars. This insulation may be formed of plasterof paris, pipe clay, or any other substance possessing suitableinsulating properties and sul'licient mechanical strength and rigidityto prevent itf'rom becoming displaced under the conditions of service,and which is of such nature that it will be worn away by the brushfriction at substantially the same rate as are the conducting commutatorbars. The other portion of the insulating material between theconducting bars which may be of sheet mica, leather board, etc, servesas the means principally relied upon to space the bars apart and withthe bars to form a rigid structurewhen the commutator is assembled.

Commutators constructed in this manner possess practically all of theadvantages of a commutator built in the ordinary manner with sheet micainsulation, while the insulation which is engaged by the brushes is ofsuch a nature that it will be worn away at substantially the same rateas are the commutator bars. The outer insulating portion prevents theaccumulation of dirt, copper dust, etc., between the outer portions ofadj acent bars, and insures a smooth brush engaging commutator surface,and consequently noiseless and smooth running operation. The outerinsulating portion also prevents moisture, etc., from coming intocontact with the inner insulating portions, an important considerationwhen the inner insulating portions are formed of leather board or othersubstances which may be ail'ected by moisture.

The features of novelty which characterize my invention are pointed outwith par ticularity in the claims annexed to and forming a part of thisspecification. For a better understanding of my invention, however,reference may be had to the accompanying drawings and descriptive matterin which I have illustrated and described some of the forms in which myinvention may be embodied.

Of the drawings, Figure l is a side elevation partly in section of acommutator constructed in accordance with my invention; Fig. 2 is apartial end elevation showing a portion. of the bars and insulationbetween them of the commutator shown in Fig. 1; Figs. 3 and 4 are viewssimilar to Fig. illustrating modifications ofthe bars which may be usedin the commutator shown in Fig. 1; and Fig. 5 is an elevation partly insection illustrating the application of my invention to a different typeof commutator.

In the construction shown in Figs. 1 and 2, 1 represents the shaft of adynamo electric fiiachineiipon which is mounted the commutator shell 2.The commutator shell is provided at one end with a flange portion 3formed with an annular clamping jaw 4. An end member 5 formed with aclamping jaw 6 opposing the jaw 4 is mounted on the opposite end of theshell. he commutator bars or segments 7 which may be formed of copper inthe usual manner are provided on their inner edges with integralundercut tenon portions 8 which are gripped between the jaws 4 and 6.The bars 7 are locked in place between theclamping jaws by means of anut 9 threaded on the commutator shell. Suitable insulation 10 separatesthe commutator bars from the flange 3 and end member 5.

Insulating material in the form of strips 11 of sheet mica, leatherboard, or other material possessing proper mechanical insulatingproperties, separate the portions of the commutator bars within the lineAA in Fig. 2 which represents the surface of the commutator when it isworn down to the stage at which it becomes necessary to provide newbars. In the construction shown in Figs. 1 and 2, opposite sides of thestrips 11 are parallel. It will be understood that the strips 11 aresubstantially similar in outline to the portion of the commutatorsegments with which they are in contact, each being formed with a tenonsimilar to the tenons 8.

The spaces between adjacent commutator bars beyond the line AA arefilled with insulating material 12 which'may be plaster of paris, amixture of plaster of paris and alum, pipe clay, or other suitablematerial as before mentioned. In the construction shown in Figs. 1 and2, the surface of adjacent commutator bars beyond the line AA are shapedto form tapered spaces which the insulation 12 fills, the wide edge ofeach recess being the inner edge. The insulation 12 is ordinarily notput into place until after the tenon portions of the commutator bars 7and strips 11 have been firmly clamped in posi tion between the annularaws carried by the end members 3 and 6. After the commutator bars are inplace the insulation 12 may be inserted in any suitable manner as byforcing it into place in a suitable press, while the insulating materialis in a plastic condition.

\Vhile the tapered recess construction for the reception of theinsulating material 12 is advantageous as it greatly decreases theliability of the insulation 12 becoming displaced by the operation ofthe commutator, it is not always necessary to shape the bars in thismanner. For instance, adacent surfaces of adjacent commutator bars maybe plane and parallel as shown in Fig. 3 or recesses or grooves 13 maybe formed in the sides of the commutator bars at or about the line AA asshown in Fig. 1. In any case,

the liability of the commutator throwing the insulating material 12 outwhen in service is diminished by roughening the sides of the commutatorbars as by a sand blast operation.

In Fig. 5 I have illustrated a construction in which the commutator barsor segments 14 in the form of prisms or bars with parallel edges aresecured to their supporting shell by one or more rings 15 which areassembled while hot and shrunk into position. In this construction thestrips of insulating material 11 corresponding to the strips 11 of theconstruction first described are formed with cars 16 which project abovethe line AA beneath the rings 15. In this construction also the spacesbetween adjacent commutator bars not occupied by the insulating material11 is filled by insulation 12 which may be similar to the insulation 12.

It will be readily apparent to all those skilled in the art that changesmay be made in the form of the embodiments of my invention disclosedwithout departing from the spirit of my invention, and I do not wish theclaims hereinafter made to be limited to the particular constructionsdisclosed more than is made necessary by the state of the art.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. The combination with the segments of a commutator, of insulationwhich is comparatively easily worn away by the commutator engagingbrushes between those portions of adjacent segments which are worn awayby the brushes during the life of the commutator, and tougher insulationbetween other portions of said segments.

2. In a commutator, a pair of adjacent commutator bars and insulationbetween them in two portions, one portion adjacent the brush engagingedges of the bars being formed of material which is readily worn away bythe commutator engaging brushes, and the other portion of toughermaterial.

3. In a commutator, bars or segments each formed with a tenon,supporting jaws between which the tenons are clamped, and insulationbetween each adjacent pair of lzars in two port-ions, an inner portionof tough material formed with a tenon similar to the tenons on thecommutator bars, and an outer portion formed of material which is lesstough.

1. In a commutator, a pair of adjacent bars, insulation between them intwo portions, one portion adjacent the brush engaging surface of thebars of plaster of paris, and the other portion of tougher material.

5. In a commutator, bars or segments formed with tenons, supporting jawsbetween which the tenons are clamped, insulation between each pair ofadjacent bars in two portions, an inner portion of tough ma terialformed. with a tenon similar to the ten- 0115 011 the commutator bars,and an outer ti f nedpf material less tough, the portions of ad acentsurfaces of adjacent commutator bars between which the outer p rtio f igpating material is located being pr vid d with means to facilitate theretention of id i ulating material.

6 I a mutator, bars or segments f d ith nons, supporting jaws betweenwhi h the tenons are clamped, insulation between eac pair of adjacentbars in two portions, an .1ner portion of leather board formed with a'tenon similar to the tenons on the commutator bars, and an outer portionformed of material less tough.

7. In a commutator, a pair of adjacent conductor bars and a layer ofinsulation between said b ars, said layer being composed of LOUIS E.UNDERWOOD.

Witnesses:

JOHN A. MoMANUs, Jr., HENRY O. WESTENDARI.

